1. Field of the Invention
The present invention relates to an ink for inkjet recording having excellent stability, high coloring on regular paper, high gloss on gloss paper and excellent discharge stability from an inkjet head.
2. Description of the Related Art
Inkjet recording is a process that ejects an ink as small droplets from a minute nozzle to record characters or images on a surface of a recording medium. Techniques of inkjet recording which have been put into practical use include: a method of converting electrical signals to mechanical signals with an electrostrictive element and intermittently ejecting an ink stored in a nozzle head to record characters or images on a surface of a recording medium; and a method of bubbling an ink stored in a nozzle head by rapidly heating that part of the ink which is located very close to the orifice and intermittently ejecting the ink based on the volume expansion caused by the bubbling to thereby record characters or images on a surface of a recording medium. An ink for inkjet recording, when used in printing onto a paper as the recording medium, is required to have characteristics such as no blurring, good drying characteristic, uniformity of printability, and no mixture property with adjacent colors in multicolor printing such as color printing.
In the conventional ink, particularly in a variety of kinds of ink using a pigment, the wettability of the ink to the surface of a paper is suppressed by mainly controlling the permeability, and print quality is secured by confining ink drops near the surface of the paper. However, when the wettability to the paper is suppressed in an ink, the extent of blurring varies according to paper types. Particularly, when printing onto a recycled paper which has various components mixed therein, the blurring occurs due to the difference in wettability characteristics of the ink to each of the components. In addition, it takes relatively a long time to dry the printing using such an ink and adjacent colors tend to be mixed in multicolor printing such as color printing. There is another problem that rubbing resistance is worsened when a pigment is used as a color material in an ink, since the pigment remains on the surface of a paper.
In order to solve these problems, the enhancement of the permeability to a paper of the ink has been attempted, and there have been examined the addition of diethylene glycol monobutyl ether (U.S. Pat. No. 5,156,675, specification), the addition of Surfynol 465 (manufactured by Nissin Chemical Industry Corporation) as an acetylene glycol system surfactant (U.S. Pat. No. 5,183,502, specification), or the addition of both the diethylene glycol monobutyl ether and the Surfynol 465 (U.S. Pat. No. 5,196,056, specification). Or the use of ethers of diethylene glycol for ink has been examined (U.S. Pat. No. 2,083,372, specification).
It is generally difficult to improve the permeability of an ink using a pigment while securing the dispersion stability of the pigment, and available penetrating agent is limited for such an ink. Therefore, some conventional combinations of the glycol ether and pigment include an example in which triethylene glycol monomethyl ether is used for the pigment (Japanese Published Unexamined Patent Application No. H56-147861), and an example or the like using ethers of ethylene glycol, diethylene glycol or triethylene glycol (Japanese Published Unexamined Patent Application No. H09-111165).